Section 116A. The department, subject to rules and regulations approved by the executive office of health and human services or a governmental unit designated by the executive office, may provide for the care and treatment of persons suffering from chronic rheumatism for a period not exceeding six months in case of any one such person, and said department may enter into contracts with one or more existing hospitals within any metropolitan district for the care and treatment of such patients; provided, that not more than twenty-five such patients may be cared for or treated under this section at any one time.